Thrust Reverser Effectiveness on High Bypass Ratio Fan Powerplant Installations

The use of high bypass ratio engines for future transports presents the opportunity to improve greatly the operational use of thrust reversers. By eliminating the gas generator reverser, or by merely spoiling the thrust of the hot gas stream, the need for reducing power due to hot exhaust ingestion can be alleviated. Engines of the 8:1 bypass ratio class can achieve today's level of reverse thrust effectiveness by reversing only the fan stream. Engines of the 3:1 bypass ratio class require fan stream reversal plus spoiling of the gas generator exhaust.

An analysis is presented indicating the desired effectiveness level for the individual fan and gas generator reversers. Design features and model testing of a particularly promising type of fan thrust reverser are discussed in detail. Test results are presented which provide information for the designer and which relate some features of fan thrust reverser geometry to performance.